Chemical mechanical planarization (CMP) is a process of smoothing surfaces with a combination of chemical and mechanical forces. The process uses an abrasive and a corrosive chemical slurry, in conjunction with a polishing pad and retaining ring to polish layers of a semiconductor structure. The pad and wafer are pressed together by a dynamic polishing head and held in place by a plastic retaining ring, while the dynamic polishing head is rotated. This removes material and tends to even out any irregular topography, making a layer of the semiconductor structure substantially flat or planar. This may be used to set up the layer of the semiconductor structure for the formation of additional circuit elements.